1. Field of the Invention
This invention relates to an optical plate, more particularly to an optical plate with microstructures.
2. Description of the Related Art
An optical plate is mainly used to change and guide a traveling direction of light. As shown in FIG. 1, a conventional optical plate 1 includes a substrate 10 and a plurality of microstructures 12 that are formed on the substrate 10 and that define a light emitting surface 11.
The microstructures 12 are parallelly adjacent to each other, and each of the microstructures 12 includes a convex portion 121 that has a cross-sectional area decreased gradually in a direction away from the substrate 10. The convex portion 121 of each of the microstructures 12 has a triangle shape or a sector shape in cross section.
The optical plate 1 is a light guiding medium in a backlight module (not shown). When the optical plate 1 is used in an edge type backlight module of a LCD device, the same can guide the direction of the light, and improve light uniformity of the LCD device. In the backlight module, a light source (such as a plurality of LEDs) is disposed at one side of the substrate 10. Light emitted from the light source enters into the optical plate 1, is reflected continuously in the optical plate 1, and is then refracted by the microstructures 12 for emitting the light outwardly. Since a plurality of LEDs are used as the light source and emit light into the optical plate 1 from one side of the substrate 10, areas between adjacent LEDs would have lower light intensity, thereby resulting in a hotspot problem.
Since the optical plate 1 is used to guide the light to emit outwardly and smoothly and is a main controlling factor for light uniformity, a pattern of the microstructures 12 would influence the light uniformity.